Apple Social Sign-In in .Net Core Web API - How to Access User's Email

We trying to implement social sign in with apple in a project which has a .Net Core Web API and a Reactjs SPA. Due to the response type and response mode limitations, from the frontend, we can only obtain an authorization code from apple on a successful sign in.

We can validate this authorization code in the backend with the following logic. Also in the response, it contains id_token where we can access some other info, but not the Email. What we are planning to do is, if the authorization code is valid and a user with the same email exists (email is the username), it authenticates the user and returns Auth JWT Token as per inbuilt authentication/authorization engine which has been implemented using asp.net core Identity framework.

    var clientSecret = CreateJwtToken();

    var data = new Dictionary<string, string>
    {
         { "client_id" , "xxx.xxxxx.com" },
         { "code" , authCode },
         { "scope" , "email" },
         { "grant_type" , "authorization_code" },  
         { "redirect_uri", "http://6c52b7b4xx.ngrok.io/login/apple" },  
         { "client_secret", clientSecret }
    };
    
   var formdata = new FormUrlEncodedContent(data);
    
   var res = await client.PostAsync("https://appleid.apple.com/auth/token", formdata);
    
   var authToken = await res.Content.ReadAsStringAsync();
    
   var responseJSON = JObject.Parse(authToken);
   var id_token = responseJSON.GetValue("id_token").ToString();

I'm not sure I'm missing something here. Is there a way that we can access the user's email in the backend? If not, is there a better way of implementing authentication with apple?

Thanks